1. Field of the Invention
The present invention relates to a positioning pivot which maintains a rotational position after being manually rotated, and more particularly to a friction adjustable positioning pivot whose friction is manually adjustable before it is used for different loads.
2. Description of the Prior Art
Positioning pivots are commonly used in many casing structures such as a notebook computer. FIG. 5 illustrates a conventional positioning pivot in cross-sectional view used in any pivotable casing structure. The conventional positioning pivot comprises a first shaft 90 connected to a cylinder 91, a resistance tube 92 made of engineering plastic being received in the cylinder 91, and a second shaft 93 being received in the resistance tube 92. The first shaft 90 and the second shaft 93 are in alignment with each other and are allowed to be rotated with respect to each other. The resistance tube 92 has an outer periphery in contact with an inner periphery of the cylinder 91 and an inner periphery thereof in contact with the second shaft 93. Therefore, the second shaft 93 is pivotable with respect to the resistance tube 92 and the resistance tube 92 is pivotable with respect to the cylinder 91. Since the cylinder 91 is firmly connected to the first shaft 90, the resistance tube 92 is also pivotable with respect to the first shaft 90. Normally the first shaft 90 is attached to a cover such as the screen panel of a notebook computer and the second shaft 93 is attached to a base such as a main body of the notebook computer or vice versa. The first shaft 90 can be rotated to a required angle with respect to the second shaft 93 and the rotated angle can be retained due to a resistance resulted from the resistance tube 92. It should be noted that the outer periphery and the inner periphery of the resistance tube 92 each respectively contributes friction against the cylinder 91 and the second shaft 93. Therefore, in practical use, the cover connected to the first shaft 90 can be pivoted to a required angle with respect to the main body connected to the second shaft 93. However, the conventional pivot can only provide a constant resistance regardless of different loads, therefore it is not suitable for different loads. For example, the resistance tube 92 may retain one kind of cover in a required pivoted angle with respect to the main body, yet it can not retain another cover which is relatively heavier than the previous cover.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional pivot.